1. Field of the Invention
The present invention relates to computer networks. More particularly, it relates to an automatic multi-rate wireless/wired computer network using a combination of wireless communications and an AC power network.
2. Prior Art
The ability to provide cost effective performance solutions for computer networks is consistently being sought by the computer industry. To date, there is not a single device on the market that can handle even the simplest task of wireless control in a broad sense. There are a few single application products that address very specific areas such as wireless mice, or wireless LAN.
The wireless products that have been brought to market are unreliable, and are not as good as a wired product, no matter what their claim. In addition, the automation of these products is not existent. That is, they generally require extensive user intervention to install, configure and get running. In addition, the market has demonstrated that network systems, and additional implementations must be transparent to the user.
Currently, there is not a product on the market that allows the use of the appropriate radio solution (i.e., speed MAC/protocol for a particular need that is flexible enough to cover most other needs as well.) For example, a user does not need a high cost radio and associated elements for low cost type applications (e.g., a mouse), but that is necessary for high-speed LAN access. Thus, there is a need for these different systems to be rolled into one, such that multiple modulation schemes for the varying complexity of devices can be implemented in a single piece of hardware, and whose cost is proportional to the function currently being added.
Historically, there are a limited number of modulations available and systems are typically built around one. Typical modulations used include; AM. And the related QAM FM, and the related FSK, GMSK, MFSK PSK and the related BPSK, QPSK, and M-ary PSK. Within the confines of the FM domain are the related FSK, GMSK, and M-ary FSK. In addition, the PSK modulation family is directly related to FSK via mathematical relation of differentiation or integration for the reverse relation.
Beyond these modulations, there is another family now popularized as Spread Spectrum. These have the properties of robust communications while in harsh electronic environments, such as near other radio systems, or interference such as a microwave oven, etc. They also allow transmission of higher power levels since their output is "spread" over many frequencies. Essentially, there are two spread spectrum modulations, both of which are related to the FM and PSK families discussed earlier. The FM relation is what is called Frequency Hopping (FH), whereby data is mapped into the frequency domain and spread over 80 or more frequencies as illustrated in FIG. 1. The pseudo random mapping is a known sequence to both the transmitter and receiver, therefore the receiver can un-map the hopped frequencies back to the original data sequence. The second family of PSK related modulations is called Direct Sequence Spread Spectrum (DSSS). Here the original data sequence is re-mapped into phase changes rather than frequency changes. These show up in the frequency domain as looking like a Sinc function or sin x/x as shown in FIG. 2.
The FCC imposes certain restrictions on the use of both transmitted power and bandwidth. Power is related directly to the operable distance a device can work over, while bandwidth affects the data rate or speed of communications. One can only push the data rate up until the limit of the FCC bandwidth of a particular band is reached, then additional techniques need to be implemented to go beyond that, such as higher complexity modulations like M-ary PSK, or M-ary FSK or data coding techniques.
Cost sensitivity is also a clear market driven requirement. The cost must be proportional to the function the system provides. A system that can provide simple mouse interface must not cost much more than one would have to pay for the wired equivalent, yet the system must be expandable to higher level of function and speed with proportional cost.
Thus, it is apparent that there is a need for a wireless computer system which includes both protocol and hardware, which is capable of multiple modulation schemes and is simple in setup, operation and cost. The network must be expandable as the user requires, and must be transparent to the user. This means, after software installation, the user does nothing except turn on the components and they do the work of configuration within the wireless environment around a computer and the AC power network. The computer will be able to implement the simplest of tasks such as the wireless mouse and joystick to the more complex task of wireless local area networks.